The present invention relates to a concrete composition for an overlay method of construction and also to a cured product thereof.
An overlay method of construction using stylfiber reinforced concrete (SFRC) has been proposed as a method of construction for repairing, for instance, a landing strip. In this overlay method of construction, the surface of a pavement is cut off by a desired thickness, the cut surface is treated by shotblasting in which a hard ball is struck against the cut surface, and a newly paved plane (surface layer) is formed on the cut surface.
An overlay method of construction not by means of surface treatment using only shotblasting in which a hard ball is struck against the cut surface but by means of the following surface treatment is proposed in Japanese Patent Application Laid-Open (JP-A) No. H9-71902. In this overlay method of construction, first a water jet which jets high pressure water is used to form relatively large irregularities (uneven surface) on a deteriorated paved surface and/or paved layer and in succession, shotblasting in which small grains are jetted is used to form small irregularities on the above surface with large irregularities thereby forming a complex irregular structure having relatively small irregularities further on a surface with relatively large irregularities and on the complex irregular structure, a newly paved plane (surface layer) is formed.
The invention described in JP-A No. H9-71902 solves the problem that only the process in which the surface of a pavement is cut and a newly paved plane (surface layer) is formed on the cut surface results in the fact that bonding between the existent paved layer and the new surface layer is easily damaged by repetitive action of compressive stress and tensile stress. In the invention, therefore, an irregular structure is formed on the surface of an existent paved layer and a new surface layer is fitted to the irregular structure to increase the bonding strength between the existent paved layer and the new surface layer thereby extending the life of the repaired paved plane.
As aforementioned, the invention proposed (or described) in JP-A No. H9-71902 has an intention to improve the bonding strength between an existent paved layer and a new surface layer by fitting of the irregularities to each other.
However, it comes to be understood that only insufficient bonding strength is obtained only by the fitting of the irregularities in the method proposed in JP-A No. H9-71902.
To state in more detail, it has been found that even if the surface treating technique proposed in JP-A No. H9-71902 is adopted to form a new surface layer on an existent paved layer, on which irregularities are formed, by using a conventional concrete composition, the bonding strength between the existent paved layer and the new surface layer is weak depending on the composition of concrete forming the new surface layer and on the detail of the cured product.
A first object of the present invention is to provide a concrete composition for an overlay method of construction which gives strong bonding strength between an existent paved layer and a new surface layer and is resistant to exfoliation and also to provide its cured product.
A second object of the present invention is to provide a concrete composition for an overlay method of construction which is resistant to cracking and wear of a new surface layer formed on an existent paved layer and also to provide its cured product.
A concrete composition for an overlay method of construction according to the present invention is a concrete composition used in an overlay method of construction for improving a deteriorated paved surface and/or a paved layer, the concrete composition comprising a cement, a shrink-reducing agent, an expanding agent, a high performance AE water-reducing agent and an AE agent, wherein the cement is a low heat portland cement.
A concrete composition for an overlay method of construction according to the present invention is a concrete composition used in an overlay method of construction for improving a deteriorated paved surface and/or a paved layer, the concrete composition comprising a cement, a shrink-reducing agent, an expanding agent, a high performance AE water-reducing agent, an AE agent and a retardant, wherein the cement is a normal portland cement.
Particularly, the concrete composition for an overlay method of construction according to the present invention attains the first and second objects when it is used in an overlay method of construction in which a water jet which jets high pressure water is used to form relatively large irregularities (uneven surface) on a deteriorated paved surface and/or paved layer and in succession, shotblasting in which small grains are jetted is used to form relatively small irregularities on the above surface with large irregularities thereby forming a complex irregular structure having relatively small irregularities further on a surface with relatively large irregularities and on the complex irregular structure, a newly paved plane (surface layer) is formed.
A cured product of the concrete composition for an overlay method of construction according to the present invention satisfies at the same time the following requirements: a compressive strength larger than a prescribed value and an expansion volume greater than a prescribed value, thereby attaining the first and second objects.